Improved early and long-term detection of bovine lentivirus by a nested polymerase chain reaction test in experimentally infected calves.

A nested polymerase chain reaction (PCR) test was developed to examine infection with the bovine lentivirus, bovine immunodeficiency-like virus (BIV), in cattle. Primers were designed to amplify 2 separate regions of the pol and env segments of the BIV genome. Two calves were experimentally infected with an isolate derived from the original strain of BIV, R29, or with a recent field isolate, FL491. Serial blood samples were collected and examined by virus isolation, protein immunoblot, and nested PCR. The nested PCR test detected BIV infection by 3 days after inoculation, earlier than the other 2 methods, and continued to identify infected cattle 9 to 15.5 months after inoculation, even when results from virus isolation and serology became negative. Nested PCR also detected multiple-size env products in samples obtained later in the infection from the calf that received FL491, giving evidence that viral quasispecies were selected during in vivo replication of the virus. Results indicated that the nested PCR test is more sensitive than virus isolation or serology for the detection of BIV infection in cattle.